One time I toped up some oil, put the oil back in the garage and shut my engine lid, thing is I forgot to tighten the oil cap, driving to my mates and driving back to my house I noticed my car was blowing abit of smoke, jumped out and theres oil all over the boot and rear window, and the cap is gonzo.
Spent the best part of a day degreasing it.
another one was my mates car was misfiring so he pops the bonnet and looks around,
"ahh thats the problem, a plug lead is loose"
so he goes and grabs it, while the car is running...
absolutely shocking (boom, tish)